Joaquim Teixeira de Assis

Rio de Janeiro State University | UERJ · Departamento de Engenharia Mecanica e Energia

X-ray computed microtomography (μCT or micro-CT) allows a nondestructive analysis of samples, which helps their reuse. The X-ray μCT equipment offers the user several configuration options that change the quality of the images obtained, thus affecting the expected result. In this study, a methodology for analyzing X-ray μCT images generated by the...

X-Ray Computed Microtomography (µCT or micro-CT) allows a non-destructive analysis of samples, which helps their reuse. The X-Ray µCT equipment offers the user several configuration options that change the quality of the images obtained, thus affecting the expected result. In this study, a methodology for analyzing X-Ray µCT images generated by the...

https://doi.org/10.26415/2572-004X-vol3iss2p402-412 This paper applies the Standard Scale Invariant Feature Transform (S-SIFT) algorithm to accomplish the image descriptors of an eye region for a set of human eyes images from the UBIRIS database despite photometric transformations. The core assumption is that textured regions are locally planar an...

The main objective of this project is to define a methodology for sediments characterization, imaging the material deposited in the tanks or in locu. In this project it was evaluated 3D reconstruction of the simulated planar images and the definition of limitations of the technique by simulating the sediment images using the Monte Carlo toolkit XRM...

The objective of this project is to compare XRMC version 6.5.0-2 to Geant4 version 10.02.p02 and the results of both Monte Carlo tools to experimental data collected by using three different mammographs for dosimetric applications in mammography (external dosimetry), validating XRMC and Geant4 for dosimetric applications in mammography. To validate...

The objective of this project is to validate for macroscopic quantities the xrmc toolkit version 6.5.0-2 [1], comparing against experimental data collected for dosimetric applications in mammography (external dosimetry). The xrmc is focused on X-ray photon transport simulation, and makes extensive use of variance reduction techniques. To validate t...

In this paper, a fresh procedure to handle image mixtures by means of blind signal separation relying on a combination of second order and higher order statistics techniques are introduced. The problem of blind signal separation is reassigned to the wavelet domain. The key idea behind this method is that the image mixture can be decomposed into the...

Resumo: A microtomografia computadorizada (computed microtomography-µCT) permite uma análise não destrutiva de amostras, o que possibilita sua reutilização. Equipamentos de µCT oferecem ao usuário diversas opções de configurações que alteram a qualidade das imagens obtidas afetando, dessa forma, o resultado esperado. Neste estudo foi desenvolvida u...

Physiological oral mechanical forces may play a role on the progression of enamel carious lesions to cavitation. Thus, the aim of this study was to describe, by 3D finite element analysis, stress, and strain patterns in sound and carious enamel after a simulated occlusal load. Micro-CT based models were created and meshed with tetrahedral elements...

Computed tomography is a nondestructive technique that allows the visualization of internal structures of a sample. However, the attenuation coefficient of a material to radiation, shown in grayscale levels, can be interpreted as the combination of parameters of density and atomic number. Thus, the separation of different structures of equal attenu...

Many objects of common use (tools, utensils, metals, knick-knacks, dishes and glasses) and artifacts (for example paintings of all types) are composed of two or more layers. In many cases, it would be useful to determine the correct location, composition and thickness of the various layers.Non-destructive and non-invasive methods are described, bas...

This in vivo study aimed to evaluate the influence of contact points on the approximal caries detection in primary molars, by comparing the performance of the DIAGNOdent pen and visual-tactile examination after tooth separation to bitewing radiography (BW). A total of 112 children were examined and 33 children were selected. In three periods (a, b,...

At present work we propose the use of multi-core processors to parallelize and speed up the Feldkamp, David e Kress (FDK) algorithm for tomography image reconstruction. Are commented the bases of computed tomography and the image reconstruction process. Proposes a computational implementation of the algorithm and its parallelization. The serial and...

Neste trabalho são discutidas as vantagens e a viabilidade do uso do pó proveniente do processamento de resíduos têxteis, descartados por confecções e indústrias de tecido, e estudada a sua utilização na substituição parcial do agregado miúdo natural (areia) na produção de concretos de cimento Portland convencionais. Foi convencionada uma relação á...

Microtomographic (µCT) and thin section (TS) images were analyzed and compared regarding porosity and its distribution along the samples. The results show that µCT, although limited by its resolution, shows relevant information about the distribution of porosity and quantification of connected and non-connected pores. TS have no limitations concern...

Duplex stainless steel is an example of composite material with approximately equal amounts of austenite and ferrite phases. Difference of physical and mechanical properties of component is additional factor that contributes appearance of residual stresses after welding of duplex steel plates. Measurements of stress distributions in weld region wer...

Hydrogen Peroxide is a bleaching agent that is capable of oxidizing a wide range of colored organic materials, causing discoloration and hence bleaching of the substrate, but some authors have reported the occurrence of side effects related to bleaching of the tooth structure, such as changes in superficial morphology. In this experiment, 6 bovine...

In recent years, bone quantification led to a deeper knowledge of the 3D microarchitecture. In this study the bone architecture of rats was investigated based on 2D/3D morphometric analysis using microcomputed tomography, aiming at determining the effect of the image acquisition pixel on the quality of some 2D/3D morphometric parameters, such as po...

Duplex stainless steel is a material that attracts great interest of different branches of engineering and industry because of its combination of good structural and mechanical characteristics and high corrosion resistance. The microstructure of duplex steel presents an example of composite material with approximately equal amounts of austenite and...

5. OPERAÇÕES EM IMAGENS NO DOMÍNIO ESPACIAL As imagens aqui tratadas nesse tópico são imagens digitais em forma de matrizes n x m em que cada ponto é um número inteiro que representa uma cor, e sobre os quais pode-se efetuar operações lógicas (AND, OR, NOT) e/ou aritméticas (+, -, x, /). Essas operações podem ser efetuadas pixel a pixel ou sobre um...

The aim of this in vitro study was to evaluate the efficacy of X-Ray fluorescence technique on the measurements of de-remineralization in bovine enamel subject to erosion and treated with three products. We obtained 15 specimens (CP) who were randomly divided into 3 groups. All teeth were initially evaluated to obtain the count of elements phosphor...

In this paper a general method based on energy-dispersive X-ray fluorescence (EDXRF) analysis has been 32 tested to assess its possible use as a tool to reconstruct the structure and determine the thickness of two 33 and/or multi-layered materials. The method utilizes the X-ray intensity ratios of Ka/Kb or La/Lb peaks (or 34 the ratio of these peak...

This manuscript applies the Scale Invariant Feature Transform (SIFT) algorithm to determine image descriptors of an eye region for a set of human eyes imageries from the UBIRIS database even in the presence of photometric transformations. The main rationale is that textured regions are locally planar and stationary. A descriptor with this kind of i...

The aim of the this study was to quantitatively evaluate in three-dimensional (3D), the porosity degree of three improved silicate-based endodontic repair cements (iRoot BP Plus(®) , Biodentine(®) , and Ceramicrete) compared to a gold-standard calcium silicate bioactive cement (Pro Root(®) MTA). From each tested cement, four samples were prepared b...

Resumo Português: Nesta dissertação é apresentado o desenvolvimento de uma ferramenta computacional para o processamento de pares de imagens estereoscópicas obtidos por câmeras aéreas métricas e não métricas. O programa foi desenvolvido na linguagem C++ e foi utilizado a biblioteca OpenGL. O resultado obtido é uma imagem tridimensional de onde pode...

Neste trabalho apresentamos a computação quântica como o novo modelo decomputação. Esta nova interpretação da realidade, vista sob os olhos da Física Quântica,traz a possibilidade da construção de dispositivos físicos que superam as máquinas atuais e podem permitir a solução de problemas antes intratáveis. Sob esta ótica a criptografiaquântica surg...

Charged particle interactions with matter have been continuously studied by simulations based on the Monte Carlo method. In particular, the Geant4 toolkit allows to develop and test new technologies by computer simulations. A proton computed tomography (pCT) prototype has been developed at the Lorna Linda University Medical Center (LLUMC), Californ...

Histograma no intervalo [0,L-1] é uma função discreta p(r k)=n k /n, onde r k é o k-ésimo nível de cinza, n k é o número de pixels na imagem que tem o nível de cinza k, n é o número total de pixels da imagem, e k=0,...,L-1. Figura 1 – Histograma de níveis de cinza da imagem padrão cameraman. Figura 2 – Histograma de níveis de cinza da imagem padrão...

Different physical, mechanical and chemical processes, such as: ion implantation, oxidation, nitridation and others create on the surface of materials residual stress state, characterized by high level and strong gradient. X-ray diffraction method widely used for stress measurements has some difficulties in interpretation of experimental data, when...

Dental caries is a biofilm-mediated disease leading to cavitation and tissue loss. While mineral dissolution in enamel and dentin are considered the main factors in the progression from non-cavitated to cavitated lesions, the role played by the oral mechanical forces on cavity formation has been overlooked. Objective: To describe, by a 3D finite el...

The research of polymer blends, or alloys, has experienced enormous growth in size and sophistication in terms of its scientific base, technology and commercial development. As a consequence two very important issues ar ise: the increased availability of new materials and the need for materials with better performance. Polymer blends are polymer sy...

Bone quality is an evaluation index often applied in order to interpret clinical observations made upon bone health, such as bone mineral density, micro and macro architecture, and mineral content. Conventional inspection techniques do not provide full information on trabecular bone quality. This study shows the high resolution potential and the no...

Monte Carlo simulations are essential for the support of particle experiments and developments of novel particle registration systems ranging from detectors developed for high-energy physics experiments at CERN to those for medical tomography. For proton beams, popular Monte Carlo codes like TRIM/SRIM, MCNPX and GEANT4 generate very similar final e...

Proton beams in medical applications deal with relatively thick targets like the human head or trunk. Thus, the fidelity of proton computed tomography (pCT) simulations as a tool for proton therapy planning depends in the general case on the accuracy of results obtained for the proton interaction with thick absorbers. GEANT4 simulations of proton...

XXXIV edition of the Brazilian Workshop on Nuclear Physics, Foz de Iguaçu, Parana state, Brasil 5-10 June 2011 1 Speaker PoS(XXXIV BWNP)085 Microtomography in species of Proceratophrys bigibbosa Francielle Ahmann 2 The Proceratophrys bigibbosa species group is characterized by the presence of postocular swellings and absence of hornlike palpebral a...

The GEANT4 simulations are essential for the development of medical tomography with proton beams — pCT. In the case of thin absorbers the latest releases of GEANT4 generate very similar final spectra which agree well with the results of other popular Monte Carlo codes like TRIM/SRIM, or MCNPX. For thick absorbers, however, the disagreements became...

The pCT deals with relatively thick targets like the human head or trunk. Thus, the fidelity of pCT as a tool for proton therapy planning depends on the accuracy of physical formulas used for proton interaction with thick absorbers. Although the actual overall accuracy of the proton stopping power in the Bethe‐Bloch domain is about 1%, the analyti...

Characterization of trabeculae structures is one of the most important applications of imaging techniques in the biomedical area. The aim of this study was to investigate structure modifications in trabecular and cortical bones using non destructive techniques such as X-ray microtomography, X-ray microfluorescence by synchrotron radiation and scann...

In this paper, a novel technique for blind signal separation based on a combination of second order and higher order approaches is introduced. The problem of blind signal separation was solved in a wavelet domain. The main idea behind this approach is that the mixing signal can be decomposed into a sum of uncorrelated and/or independent sub-bands u...

Local perturbations around contours strongly disturb the final result of computer vision tasks. It is common to introduce a priori information in the estimation process. Improvement can be achieved via a deformable model such as the snake model. In recent works, the deformable contour is modeled by means of B-spline snakes which allows local contro...

In recent years, the 3D X-ray microcomputed tomography (3DμCT) has become a useful method to access the internal geometry based microarchitecture of bones. All measurements are based on the image quality. In this context, the aim of this work is to investigate bone quality in terms of strength parameters determined by 3DμCT. The system that was use...

In this paper, two simple principal component regression methods for estimating the optical flow between frames of video sequences according to a pel-recursive manner are introduced. These are easy alternatives to dealing with mixtures of motion vectors in addition to the lack of prior information on spatial-temporal statistics (although they are s...

This work presents the recent results of computer simulations for the low energy proton beam tomographic scanner installed at the cyclotron CV-28 of IEN/CNEN. New computer simulations were performed in order to adjust the parameters of previous simulation within the first experimental results and to understand some specific effects that affected th...

Proton computerized tomography deals with relatively thick targets like the human head or trunk. In this case precise analytical calculation of the proton final energy is a rather complicated task, thus the Monte Carlo simulation stands out as a solution. We used the GEANT4.8.2 code to calculate the proton final energy spectra after passing a thick...

The main goal of this research is to carry out a high resolution analysis in vitro of biomedical samples as well as of industrial components by Microcofus 3D X-Ray Computed Tomography. This technique was able to provide information in a noninvasive way for different compositions, size and structure mapping out the shape and size distribution of por...

BP explores various partitioning of the visual data volume (of size W  H  F = width  height  frames) into smaller blocks and applies PCA to them individually. With BP, it is possible to take full advantage of the local linearity in the data. Clustered Blockwise PCA (CBP) BP allows us to apply PCA to large data sets faster and more notably, with...

This paper analyzes two variants of principal component analysis (PCA) for error-concealment: blockwise PCA and clustered blockwise PCA. Realistic communication channels are not error free. Since the signals transmitted on real-world channels are highly compressed, regardless of cause, the quality of images reconstructed from any corrupted data can...

Some problems arise in the case of residual stresses measurements by X-ray diffrac-tion technique when analyzed stress state is characterized by strong gradient on the surface of a material. These problems include the fact that linear dependence of the diffraction angle θ ϕ,ψ =f(sin 2 ψ) becomes nonlinear. Besides, there is broadening of diffractio...

Proton beams in medical applications deal with relatively thick targets like the human head or trunk. Therefore, relatively small differences in the total proton stopping power given, for example, by the different models provided by GEANT4 can lead to significant disagreements in the final proton energy spectra when integrated along lengthy proton...

In this work an image processing technique is use to determine the porosity of simple concrete specimen. In this material the resistance is considered the most important property, showing an idea of the concrete quality, being directly connected to the structure of the hydrated cement paste. The automatization of the methods that determine the conc...

Skin cancer is one of the most frequent tumors. When early diagnosticated, this kind of cancer reaches a high percentage of cure. But the identification of its characteristics is necessary. The characteristics to be analised are: Asymmetry (A); Irregularity border (B); Color (C) and diameter (D). The present work uses as a tool for the first diagno...

Concrete is nowadays one of the most used materials used in construction and for this purpose its properties have been more and more studied so that it can be used at its maximum performance. The mechanical strength of compression is one of the main properties of this material, knowing that it determines the quantity of load that a structure can st...

In this work an image processing technique is use to determine the porosity of simple concrete specimen. In this material the resistance is considered the most important property, showing an idea of the concrete quality, being directly connected to the structure of the hydrated cement paste. The automatization of the methods that determine the c...

Conteúdo: 1) Introdução 2) Motivação 3) Caracterização do Problema 4) Modelo 5) Resultados Experimentais 6) Conclusão e Trabalhos Futuros 7) Referências

Study of stress gradients is one of the important problems of the X-ray tensometry, especially, in the case of analysis of residual stress state arising after different modern treatments like material modifications by ion beam technologies or surface treatments by laser. These problems related directly with incompleteness of theoretical and experim...

Neste trabalho apresentamos a computação quântica como o novo modelo de computação. Esta nova interpretação da realidade, vista sob os olhos da F'isica Quântica, traz a possibilidade da construção de dispositivos f'isicos que superam as máquinas atuais e podem permitir a solução de problemas antes intratáveis. Sob esta ótica a criptografia quântica...

In this paper, we derive a principal component regression (PCR) method for estimating the optical flow between frames of video sequences according to a pel-recursive manner. This is an easy alternative to dealing with mixtures of motion vectors due to the lack of too much prior information on their statistics (although they are supposed to be norma...

In this paper, we derive a principal component regression (PCR) method for estimating the optical flow between frames of video sequences according to a pel-recursive manner. This is an easy alternative to dealing with mixtures of motion vectors due to the lack of too much prior information on their statistics (although they are supposed to be norma...

In proton treatment planning, the use of protons instead of X-rays for computerized tomography (CT) studies has potential advantages, especially for medical applications. Proton CT requires accurate measurement of the energy loss of protons passing through the object. The resolution of a proton CT scanner is determined by the resolution of the ener...

Deslizamentos são movimentos gravitacionais de massa que estão relacionados aos processos de desestabilização de encostas. No Brasil a maioria dos escorregamentos acontece devido à ação das chuvas. Os processos de instabilidade de encostas podem incluir outros fenômenos naturais e não naturais. Com o crescimento desordenado das cidades, com a ocupa...

In this work, the modified Thompson-Cox-Hastings function (TCHZ) was used in the analisys of the integral breadths obtained from the broadned X ray diffraction line profiles. These set of X ray diffraction results were calculated from the "Le Bail" fitting method, which does not require any structural information, except unit cell and resolution in...

Aluminium-silicon alloy or silurnin fabricated by powder metallurgy is a material widely used in aircraft and precision mechanics industries because of homogeneous composition and high mechanical properties. Residual stresses arising in this kind of composite material caused by the difference of thermal expansion coefficients of components have neg...

This work presents an automatic fingerprint identification system using a coefficient map in the power spectrum based on Gabor filter. This filter was created by Dennis Gabor in 1946 and is being used in many biometric technologies. The fingerprint core is found by pixel neighborhood technique. Around the core, the input image is divided in quadran...

Neste trabalho é apresentado o desenvolvimento de uma ferramenta computa- cional para o processamento de imagens estereoscópicas com o objetivo de compor uma imagem tridimensional que será utilizada para identificar poss\'\iveis áreas de risco em en- costas. São apresentados resultados preliminares de simulações para a obtenção da este- reoscopia,...

Modern surface treatment technologies, like laser treatment or surface modifications by ion beams, introduce high residual stresses characterized by strong gradients of stress distribution in the depth of treated surface. The diffraction methods of stress gradient determination based on analysis of nonlinearity of d, - sin2 dependency is not suffic...

From the x-ray diffraction theory, we know that the broadening of the reflection lines obtained from a powder sample may be related to some imperfection of the crystallite. Such broadening effect may also be caused by instrumental failures and dispersion of the length of the radiation. In this study, the micro structural parameters of two improved...

Microtectônica é a parte da geologia que se ocupa do estudo da reconstrução estrutural (evolução tectônica) e da história metamórfica do volume de uma rocha. Para tal são usadas seções extremamente finas de rochas, promovendo-se a seguir a deformação do material escolhido que pode ser gravada em imagens fotográficas ou de vídeo. Estas lâminas delga...

Proton beams can destroy tumors better than other radiation treatment options because they deliver their energy in a very accurate way, while leaving the surrounding tissue undamaged. However, it requires a very accurate prediction of the Bragg peak position within the patient's body. In existing proton treatment centers, the dose calculations are...

Although the idea of proton Computed Tomography (pCT) is not new, it is currently not available. It is still unknown if the image quality of pCT is sufficient for localizing tumors and if the accuracy of proton range calculations surpass that of X-ray CT based range calculations without significantly increasing the patient exposure. The spatial res...

Medical diagnosis can be viewed as a task that allows physicians to make predictions about features of clinical situations and to determine appropriate course of action. Medical training simulations systems provide students and novices with opportunities to practice critical tasks. The main goal of this paper is investigate the feasibility of typic...

In existing proton treatment centers, dose calculations are performed based on x-ray computerized tomography (CT). Alternatively, the therapeutic proton beam could be used to collect the data for treatment planning via proton CT (pCT). With the development of medical proton gantries, first at Loma Linda University Medical Center and now in several...

The main contribution of this work is the automation of geological tasks such as dealing with extremely thin sections of rocks submitted to deformation along finite steps of time which can be recorded in video sequences for later analysis by means of image processing and numerical analysis techniques. Markers are used in order to trace gradients of...

Conformal proton radiation therapy requires accurate prediction of the Bragg peak position. This problem may be solved by using protons rather than conventional x-rays to determine the relative electron density distribution via proton computed tomography (proton CT). However, proton CT has its own limitations, which need to be carefully studied bef...

Conformal proton radiation therapy requires accurate prediction of the Bragg peak position. This problem may be solved by using protons rather than conventional x-rays to determine the relative electron density distribution via proton computed tomography (proton CT). However, proton CT has its own limitations, which need to be carefully studied bef...

Difficulties of determination of surface stress gradients using X-ray diffraction technique are connected with interpretation of non-linearity of thetaphi,psi versus sin2psi experimental curves. The problem is that the scattering of experimental data conceals a non-linear character of sin2psi dependency and does not allow to determine correctly the...

One of characteristic feature of stress determination by X-ray diffraction technique is the possibility to analyze stress state in individual phases of a multiphase material. Duplex steel widely used in chemistry and oil refinery equipments is an example of this kind multiphase material consisting of approximately equal quantities of ferrite and au...

Conformal proton radiation therapy requires accurate prediction of the Bragg peak position. This problem may be solved by using protons rather than conventional x-rays to determine the relative electron density distribution via proton computed tomography (proton CT). However, proton CT has its own limitations, which need to be carefully studied bef...

Portable apparatus presented in this paper is an x-ray equipment permitting to carry out traditional stress determination by x-ray diffraction method both in-laboratory and in-field conditions. The portability of apparatus is achieved by construction of compact and light high voltage source coupled with special x-ray tube and using of coordinate se...

Soil and radish (Raphanus Sp) samples from areas treated with organic compost of recyclable urban garbage were quantitatively analyzed by using tube-excited energy-dispersive X-ray fluorescence analysis. Soils treated with 10, 20 and 30 t/ha of recyclable urban garbage and control soil were analyzed. The layer soils were collected at 0–5, 5–10, 10–...